As public awareness increases with respect to the environment, industry is required to make significant changes. Although industry is somewhat responsive to public opinion, government regulatory bodies are typically brought in to ensure that public needs are met. In order to do this, government sets up regulatory arms of already existing branches of entities such as the Environmental Protection Agency. These arms are given the task of putting in place policies regarding toxic waste, emissions, etc., that may effect the environment. Further, these regulatory bodies are also given the task of enforcing these regulations. One particular area that has received a great deal of attention in recent years is that of monitoring emissions of noxious gases being placed into the atmosphere by manufacturing facilities.
Typically, the technique for ensuring that noxious gases are being correctly monitored has been to implement Continuous Emissions Monitoring systems (CEM). These systems are utilized to monitor the amount of emissions such as Sulfur Dioxide (SO.sub.2), Nitrogen Oxides (NOx), Carbon Monoxide (CO), Total reduced Sulfur (TRS), opacity, Volatile Organic Carbon (VOC), and hazardous substances of all sorts. The classical way of monitoring of these emissions is to install a Continuous Emission Monitor (CEM) in the plant on each emission point source. Regulatory Agencies provide for each plant guidelines as to how the output is to be regulated, i.e., define the acceptable limit of the emissions.
The classic CEM is composed of either an in situ analyzer installed directly in the stack, or an extractive system which extracts a gas sample and conveys it to an analyzer at grade level. However, these sensors are quite expensive, difficult to maintain, and difficult to keep properly calibrated. As such, the regulations that deal with a CEM system require the sensors to be calibrated frequently, which calibration procedure can take a number of hours, due to the complexity thereof. Regulations allow a maximum downtime of ten percent for calibration. If a unit remains in operation greater than ten percent of the time with the CEM down, the emissions level is considered by the Regulators to be at maximal potential level. This results in out-of-compliance operation. Most manufactures will shut down operation rather than face the high penalties of such occurrence. One of the reasons for this is that the operation of the plant relative to the monitoring of the NOx emissions must be "truly continuous" such that no leeway is provided for faulty sensors, sensors that have fallen out of calibration, etc. One solution to this has been to utilize redundant sensors, which is a very expensive solution. Therefore, there exists a need to provide a system that does not require the presence of a sensor while still ensuring that the output of the plant is within tolerances relative to noxious emissions.